Non-woven materials consist of a loosely assembled mass of fibers that are bound together with a polymeric binder to form a self-sustaining web that can be used to produce consumer towels, disposable wipes, and other such articles. Generally anionic binders, and to a lesser extent non-ionic binders, are used to produce the non-woven articles.
Non-woven materials are particularly useful for the production of disposable wipes. Disposable wipes are used to adsorb spills, and are also used to apply solutions containing active ingredients to surfaces. Surfaces to which the solutions can be applied range from a hard surface, such as a floor, countertop or table, to a soft surface such as skin. Active ingredients may be harsh cleaning and disinfecting chemicals, or may be skin moisturizers. Wipes used to apply active ingredients may be dry wipes that must be contacted with a solution containing an active ingredient, or may be pre-moistened with one or more active ingredients.
Many useful active ingredients are cationic. Cationic active ingredients are attracted to anionic binders typically used to produce wipes. Once a cationic ingredient is attached to an anionic binder, it is difficult to release the active ingredient onto the surface. As a result, as much as half or more of the active ingredients remain attached to the wipe and are disposed of, instead of accomplishing their intended purpose. This results in the waste of costly active ingredients.
Cationic emulsion polymers are known in the art, and have been produced by either a) co-polymerizing a cationic monomer (or a monomer which can be hydrolyzed to give a cationic character) with non-ionic monomers, or b) by forming an emulsion polymer using cationic stabilizers or surfactants.
U.S. Pat. No. 4,308,189 discloses a cationic polymer emulsion in which ethylenically unsaturated monomers are polymerized in the presence of cationically-modified poly(vinyl alcohol) as the stabilizer. The cationic polymer exhibited high adhesive affinity for substances tending to be negatively charged, including as a paper strength additive or a non-woven binder. U.S. Pat. No. 5,591,799 discloses an emulsion copolymer containing N-vinyl formamide units, and in particular vinyl acetate polymers or ethylene-vinyl acetate copolymers containing cationic amine functionality.
U.S. Pat. No. 5,895,557 discloses a saturated paper for ink jet printing having either a nonionic or cationic latex binder, plus a cationic polymer which is not a binder. The use of a non-ionic binder is preferred, and no cationic binder compositions are provided in the specification or examples. No disclosure is made of application to non-wovens.
U.S. Pat. No. 5,540,987 discloses a crosslinkable emulsion non-woven binder containing N-methylol acrylamide as a crosslinking monomer. It is disclosed that the emulsion may be made with anionic, cationic or nonionic surfactants, however only anionic and non-ionic surfactants are exemplified.
There is a need for a non-woven material, made with a cationic binder for use as a wipe with cationic active ingredients. The cationic binder needs to have a combination of good absorbency, good hand, good release properties of cationic active ingredients, and good strength.
Surprisingly it has been found that crosslinkable cationic emulsion polymers can be used as binders for non-woven materials, providing good wet and dry tensile strength, good hand, and good release properties for cationic active ingredients.